An information volume flowing through a network has been exponentially increasing with an expansion of a multimedia service using the Internet, and traffic flowing through an information communication network has been largely increasing.
When the traffic has been increasing, the number of packets arriving at the same time increases, for example, within a router constructing a network. As a result, the number of times of buffering of packets increases, or load on the control of a route calculation based on a routing table increases.
For this purpose, a memory device with large power consumption, such as a high-capacity memory used for a packet buffer and a high-speed memory used for a route calculation has been disposed within the routers.
In recent years, the construction of a power-saving network is desired by a lot of users. As described above, power consumption of routers particularly has a large influence on that of the entire network, and therefore, the key to the power-saving network is offered by how the power consumption of routers is reduced.
As a conventional technique, there is proposed a technique in which a central processing unit prepares a routing table by calculating a distributing ratio of all routes on a route list and periodically updates the routing table (Japanese Laid-open Patent Publication No. 11-239181). Further, there is proposed a technique in which a communication equipment is configured by a band calculating means which calculates a transmission band from bands allocated to its own station and a destination and that allocated to all the nodes other than the destination, and a transmitting means which transmits information in the range of the transmission band (Japanese Laid-open Patent Publication No. 2002-247092).
There is considered a communication system in which when constructing a power-saving network, a slot (time slot) of a packet to be transmitted is previously allocated to transfer packets on a time-sharing base by a server side component which manages a network.
The above-described communication system is a system in which a server performs scheduling of the packet transferring such that at which time from which transmission source to which destination the packet is transferred, and then performs the packet transmission.
For example, performing the above-described control makes it possible to reduce a frequency of occurrence of a state in which a plurality of packets reach a router at the same time, and further reduce the number of times of buffering. As a result, this processing makes it possible to eliminate from the router a large-power consumption and high-capacity memory used for a packet buffer.
For example, since the router itself can be used without performing a conventional route calculation, a load necessary for the route calculation can be reduced, and a large-power consumption and high-speed memory used during the route calculation need not be used. The power consumption of routers is taken notice of and described above. The power consumption of switches constituting the network can be reduced based on the same reason.
On the other hand, it is considered that when performing scheduling, there is previously calculated an index of how many routes can be allocated to slots more so as to correspond with increase in the route accompanying a traffic variation of the network. Also, it is considered that the scheduling such that the route is allocated to slots based on the index is performed. This processing makes it possible to flexibly respond to it, even when an additional request of the route allocation is performed during the operation.
Further, after performing the allocation of the route during the operation, an index of how many routes can be allocated to slots more in the present state in which the route is allocated to slots is desired to be anew calculated to be optimized for being prepared for the next route allocation request.
However, the calculation amount for obtaining the above-described index from an arbitrary combination of routes and slots is large. Further, as a network configuration becomes more complicated, the calculation amount becomes larger. In this case, there arise the following problems. If the scheduling with a large calculation amount is performed both before the operation and in response to every additional request of a route made during the operation, in order to optimize the route allocation, real-time responses are prevented from being made and communication efficiency is reduced.